1. Field of the Invention
This invention relates to powered hand saws and more particularly, to a hand-held, gasoline-powered circular saw which is characterized by a gas-powered, trigger-operated blade drive unit connected to a conventional circular saw by means of a specially-designed adaptor. In a preferred embodiment the blade drive unit is a conventional line-trimming apparatus drive unit, and the conventional circular saw is characterized by a circular saw blade rotatably mounted in a saw housing which is connected to a drive shaft housing and adjacent gear housing. The adaptor is secured inside the drive shaft housing and includes a circular adaptor base which is typically bolted to the drive shaft housing interior, and a shaft cylinder extends from the adaptor base. The blade drive shaft connects in conventional fashion to a blade-driving gear train located inside the gear housing, and extends from the gear housing through the adaptor base and shaft cylinder, respectively, of the adaptor and projects from the drive shaft housing. The blade drive unit receives the protruding blade drive shaft and is fitted with an attachment collar which removably receives the adaptor, to connect the blade drive unit to the circular saw. The gasoline-powered circular saw is lightweight, efficient and suitable for outdoor home, farm or commercial use.
Electric circular saws are widely used in the construction industry, as well as in private workshops and homes. Since most electric circular saws require a power cord which must be plugged into a power source for operation of the saw, the saws are not truly portable and cannot be used under inclement weather conditions without jeopardizing the safety of the saw operator. These problems are particularly apparent when operation of the saws is needed for construction of roads, highways, bridges or other outdoor structures. Moreover, battery-powered saws can be adversely affected by moist or cold weather, and re-charging of the batteries can be problematic when the construction site is in a remote location with respect to a suitable battery-charging facility.
2. Description of the Prior Art
Various gas-powered saws, as well as adaptors for inter-conversion of gas-powered chain saws and circular saws, are known in the art. U.S. Pat. No. 4,121,336, dated Oct. 24, 1978, to Ellis R. Loyd, describes a "Combination Power Saw and Chain Saw and Adaptor", for converting a gasoline or electric circular saw to a chain saw, and vice-versa. The adaptor is characterized by a rectangular plate to which is attached a blade guard for receiving the conventional frame plate and blade of a chainsaw, which frame plate houses a drive sprocket for the chainsaw blade. After the blade of a conventional circular saw is removed from the circular saw frame, the circular saw frame is mounted on the rectangular plate and the saw drive shaft, connected to the engine inside the circular saw frame, is extended through an opening in the blade guard to engage the drive sprocket. The chainsaw blade is driven on the chainsaw frame plate as the circular saw engine is operated. An "Adaptor to Convert a Chain Saw to a Circular Saw" is detailed in U.S. Pat. No. 4,850,109, dated Jul. 25, 1989, to Michael A. Kerwin. The adaptor is characterized by a cylindrical collar which is secured by means of a washer and nut to the clutch housing and hub of the chain saw. A concentric opening extends through the collar, and has a ribbed, reduced diameter portion for receiving the clutch hub of the chainsaw and a threaded, enlarged diameter portion for receiving a threaded shaft extension plug. The shaft extension plug includes a face plate and a threaded shaft which extends concentrically from the face plate, for receiving a circular saw blade and a nut for securing the circular saw blade on the shaft. U.S. Pat. No. 4,876,797, dated Oct. 31, 1989, to Alvaro Zapata, details a "Reduced Vibration Portable Gas Operated Hand Saw" having a housing fitted with a carburetor and an engine, a handle which is mounted at one end of the housing and is provided with a trigger coupled to the carburetor, and a saw blade mounted at the other end of the housing. A worm gear, engaged by a centrifugal clutch which is driven by the engine, drives a rotatable shaft to which the saw blade may be keyed for rotation. Fans rotate with the clutch and saw blade, for cooling purposes. Anti-vibration elements are provided to isolate the handle and trigger from the engine. A rubber mount is interposed between the engine and housing to isolate engine vibration from the saw blade housing, saw plate, handle and trigger. A "Gasoline Engine Powered Hand-Held Circular Saw" is described in U.S. Pat. No. 5,007,173, dated Apr. 16, 1991, to Robert E. Rush. The saw includes a gasoline-powered engine which is incorporated into the body or frame of a circular saw. The engine is preferably a two-stroke engine, and is connected to a crank shaft to which the circular saw blade is mounted typically through a centrifugal clutch for rotation therewith. A throttle trigger is typically connected to the engine for controlling the engine speed. A plate is preferably provided on the circular saw frame for resting the saw on the workpiece.
An object of this invention is to provide a hand-operated, gasoline-powered circular saw.
Another object of this invention is to provide a portable, hand-operated, gasoline-powered circular saw which is capable of being used under inclement weather conditions.
Still another object of this invention is to provide a circular saw characterized by a gasoline-powered, typically trigger-operated blade drive unit which is connected to a conventional circular saw by means of a specially-designed adaptor.
Yet another object of this invention is to provide a circular saw characterized by a conventional, gasoline-powered line trimming apparatus drive unit which is connected to a conventional circular saw by means of a specially-designed adaptor having an adaptor base for attachment to the circular saw and a shaft cylinder extending from the adaptor base for engaging the line trimming apparatus drive unit.
A still further object of this invention is to provide a hand-operated, gasoline-powered circular saw which is portable, lightweight, efficient and suitable for outdoor home, farm or commercial use.